My son will take a toy and put it in the middle of his nose and make himself go crosseyed,over & over. Normal?

He is not interested in larger toys, only very small ones where he can do this. He will also take a toy and just play with it on the tips of his fingers and almost become infatuated with it, and stare at it for long periods of time. I spoke with our Dr and he said there is nothing to be concerned about. ???